Praziquantel is a broad spectrum antiparasitic agent useful for treating schistosomiasis japonica, schistosomiasis haematobia, schistosomiasis mansoni, paragonimiasis, clonorchiasis sinensis, hydatidosis, cysticercosis, sparganosis mansoni, fasciolopsiasis, trichomoniasis or the like, particularly schistosomiasis japanica and clonorchiasis sinensis. Praziquantel was firstly commercially available as “Cesol” in Germany in 1980 and became the first option for treating helminthiasis, which has the chemical structure of formula I:

DE 2504250 and DE 2508947 disclose a process for synthesizing Praziquantel using isoquinoline as starting material, which was widely used in the world. Nevertheless, the process has long processing with up to 8 steps and thus a yield as low as about 15%. During the processing, hypertoxic chemicals like cyanide is used and operation is performed under high pressure and thus this process is dangerous and prone to accident. Additionally, the process has the disadvantages like pollutants emissions and high cost for environment protection and thus is greatly limited in its industrial scaling up.
KR 2002076486 discloses a process for synthesizing Praziquantel using β-phenethylamine, chloroacetyl chloride, aminoacetaldehyde dimethyl acetal and the like as starting materials, which has relatively less reaction steps without using cyanide. However, the aminoacetaldehyde dimethyl acetal used in this process is expensive with low reactivity and selectivity and requires high reactive temperature causing side reaction and thus is not suitable for industrial production.
CN 1683346A discloses a process for synthesizing Praziquantel using β-phenethylamine, aminoacetyl halide hydrochloride, halogenated acetaldehyde acetal and cyclohexanecarbonyl chloride as starting materials with the steps of condensation, cyclization, acylation. The process is simple, environment-friendly and has less steps with total yield over 50%. However, the starting material halogenated acetaldehyde acetal is expensive with low reactivity and selectivity and the starting material aminoacetyl halide hydrochloride is not stable and prone to deterioration. Therefore, the process is not suitable for industrial production.